I. Field
The present disclosure relates generally to electronics, and more specifically to micro-electro-mechanical system (MEMS) varactors.
II. Background
MEMS is a technology used to form miniature electro-mechanical devices with mechanical moving parts. These devices may be used to implement various radio frequency (RF) circuit components such as variable capacitors (varactors), switches, resonators, inductors, etc. MEMS devices may have certain advantages over RF circuit components fabricated in other manners, such as higher quality factor (Q), lower insertion loss, better linearity, etc.
A MEMS varactor typically includes two terminals or electrodes. One terminal is typically used for a common terminal, which may be for circuit ground or some other common connection. The other terminal may be used for both an RF signal and a direct current (DC) voltage. The DC voltage may be varied to mechanically move a plate within the MEMS varactor, which may then adjust the capacitance of the MEMS varactor. The RF signal may be passed through the MEMS varactor and may have its characteristics (e.g., frequency, amplitude, etc.) altered by the capacitance of the MEMS varactor.
The 2-terminal MEMS varactor described above may be used for a low-power application with a small RF signal. In this case, the capacitance of the MEMS varactor may not be varied too much by the RF signal. However, the RF signal may be relatively large for a high-power application, such as a transmitter of a wireless communication device. If a large RF signal is applied to the MEMS varactor, then the capacitance of the MEMS varactor may be varied by a large amount due to a large root mean square (RMS) voltage of the RF signal, which may be undesirable. A MEMS varactor that can handle a large RF signal, with little or acceptable changes in capacitance due to the large RF signal, would be desirable.